If you go to the Starved Rock area, you will probably be able to take some awesome outdoor pictures of your little guy. There is a new resort in Utica, it has a water park and stuff, but I'm not sure if there are baby related water activities.
We went to Milwauskee, Sheboygan and Kohler, Wi when our son was almost 1. We stayed in Milwaukee a night or two and went to the Milwaukee zoo. We then went up towards Sheboygan & Kohler, more for ourselves, but you can walk down by the lake, there is a park on lakeshore, and a beach, or go to the shops in Kohler. There are also shops on the boardwalk in town... can't think of the name off hand where the lake is... having a mental pregnancy moment.
Kind of quiet there I guess, but it was a nice relaxing trip. We got a place with a hot tub for ourselves to enjoy also.
We use to go to Lake Geneva. You could always check out lake geneva's website and see what events they have coming up. The Cove looks like a nice place to stay, and the Grand Geneva. There are many places to stay up there.
Good luck, hope you have fun, whatever you end up doing!
M